1. Field of the Invention
The present invention relates to an articulated carrying device for carrying an object to be processed, such as a semiconductor wafer.
2. Description of the Related Art
Generally, a wafer is subjected various processes including a film forming process, an etching process, an oxidation process and a diffusion process to fabricate a semiconductor integrated circuit device. To deal with the decrease of device dimensions and the increase of device scale of semiconductor integrated circuit devices, a clustered processing system has been proposed to improve throughput and yield. The clustered processing system has one transfer chamber, and a plurality of processing devices that carries out the same process or processing chambers in which different processes are carried out connected to the transfer chamber. The clustered processing system is capable of transferring a wafer from one processing chamber to another without exposing the wafer to the atmosphere to subject the wafer continuously to the processes.
In processing wafers by the processing system of this type, a carrying device takes out a wafer from a wafer cassette placed at a wafer receiving port installed at the front end of the processing system and carries the wafer into an entrance transfer chamber. Then, an orienting device orients the wafer and the carrying device carries the wafer into a vacuum load-lock chamber capable of being evacuated. Another carrying device carries the wafer from the vacuum load-lock chamber into a vacuum transfer chamber surrounded by and connected to processing chambers and carries the wafer into the processing chambers successive to subject the wafer continuously to processes. The wafer thus processed is reversed and is returned to the wafer cassette.
The processing system of this type is provided internally with one or a plurality of carrying devices, and the wafer is transferred and carried automatically by the carrying device or the carrying devices.
The carrying device has, for example, an articulated arm capable of moving in horizontal directions, of bending and stretching, of turning and of moving vertically, and a pick connected to the distal end of the articulated arm. The articulated arm moves a pick directly holding the wafer horizontally to carry the wafer to a desired position.
The following are prior art carrying devices of the type mentioned above.
A carrying device disclosed in JP 3-19252 A/1991 (document 1) includes a pivot arm connected to a rotating shaft to convert a rotating motion into a linear motion and capable of linearly moving along a slide rail, and a pick connected to the distal end of the pivot arm and capable of holding and carrying a semiconductor wafer.
A carrying device disclosed in JP 4-129685 A/1992 (document 2) includes two articulated arms supported for turning, and combined in a frog leg mechanism so as to move in opposite directions, respectively, and pick connected to the respective distal ends of the articulated arms to carry two wafers simultaneously.
A carrying device disclosed in JP 6-338554 A/1994 (document 3) includes two rotating shafts respectively having different axes and disposed side by side, two articulated arms respectively supported on the rotating shafts, and picks respectively connected to the distal ends of the articulated arms. The picks are connected to the articulated arms at different levels, respectively, to avoid interference between the picks.
A carrying device disclosed in JP 62-106168 A/1987 (document 4) includes a linear-motion robot mechanism including a 3-dimentional linkage formed by combining two 2-dimentional linkages to exclude linearly sliding shafts that often produce particles.
Each of the carrying devices disclosed in the documents 1 to 3 has long linearly sliding parts, and/or needs a gear mechanism or timing belts to transmit driving force to the arm mechanism. Those component parts are liable to produce particles (dust) detrimental to semiconductor wafers.
Particularly, the meshed gears of the gear mechanism generate vibrations that dislocate the wafer. The timing belts are often damaged or broken.
Those problems do not arise in the carrying device disclosed in the document 4. However, since this carrying device has the 3-dimentional linkage formed by combining, for example, a 2-dimentional linkage that operates in a horizontal plane and a 2-dimentional linkage that operates in a vertical plane, the carrying device is large, needs a very large space for operation, and hence is difficult for application to a semiconductor device fabricating system.